This invention relates to the assignment of addresses to devices connected to a system by a bus, and in particular, automatic assignment of the addresses by the system in an efficient manner.
In computer systems, bus attached devices such as tapes, disk drives, monitors and other I/O devices require an address in order to be selected and used by the system. Typically, the address is predetermined and fixed by either physical location on the bus or by manual setting of switches or jumper wires. Many standard buses are not architected to use physical location to determine addresses, and manual setting of switches or jumper wires is prone to error even when performed by trained service personnel. There has been no efficient manner to accurately assign addresses without service personnel or operators actually taking the time to set the addresses for each I/O device. This is undesirable when systems are moving more toward customer setup and greater ease of use.
U.S. Pat. No. 4,360,870 to McVey describes a central processing unit which assigns addresses to I/O devices by first describing a device type and then assigning the addresses as a function of priority as established by the I/O devices of that type. This assignment scheme is dependent upon an established priority within a type of I/O device. It also requires the customer to have knowledge as to what types of devices are attached and to establish a priority for each I/O device.
IBM Technical Disclosure Bulletin, Vol. 24, No. 7B, December 1981, Programmable Assignment of Device Addresses, discloses a method of assigning addresses where the I/O devices are serially connected by a line. The addresses are assigned as a function of a priority wiring scheme and serial propagation. These methods are not available for use with many standard busses without undesirable alteration of the standard bus.